Hey readers,

This is edition 20! When I started this newsletter five months ago, I didn’t imagine the huge positive response it would get, so thank you for reading it every week and for making it worth the work.

This week there’s a bonus, an extra piece on top of the usual four.

We start in Antarctica, with a bacteria that cuts gray mold on cold-stored fruit, even when the fungus resists four fungicides. Then a study from China showing which surfactants help Metarhizium anisopliae conidia survive formulation, and a Brazilian team that spun Bacillus amyloliquefaciens fermentation broth directly into nanofibers.

In Industry, BioConsortia raised US$15 million to support the commercialization of its microbial technologies. And in The Strain, an inoculant for a forage legume that came back from the field performing better than it went in.

Let’s dive in.

Researchers at the Universidad Autónoma de Chile isolated 57 bacteria from the rhizosphere of Deschampsia antarctica, one of only two vascular plants native to Antarctica, and screened them against Botrytis cinerea at 22 °C and at 0 °C. The 0 °C test reflects the cold chain, since Chilean fruit is stored and shipped for 20 to 90 days close to 0 °C. Five isolates from the Pseudomonas fluorescens group inhibited the fungus by at least 70% at 0 °C, while reference strains of Bacillus subtilis and Bacillus amyloliquefaciens showed no detectable inhibition.

The isolates inhibited two field strains of B. cinerea, one resistant to fenhexamid and one resistant to four fungicides, as strongly as B05.10, a reference strain with no known resistance. The resistant strains remained susceptible to bacterial inhibition under the conditions tested. Genome analysis places the representative strain, AN3A02, in Aquipseudomonas as a likely new species.

AN3A02 acts through the gases it releases. In sealed plates, its volatiles slowed the fungus, and over 40 days at 0 °C they stopped it from forming sclerotia and spores. The authors have not yet identified the compounds, although the genome carries two gene clusters for hydrogen cyanide, a known antifungal volatile.

For the fruit test, inoculated fruit shared a sealed container with an agar plate of AN3A02, so the bacteria never touched the fruit. The fungus was the strain resistant to four fungicides. Blueberries stored for 45 days at 0 °C, then two days at 20 °C, showed 1.7% incidence, against 51.7% untreated and 66.7% with an SO₂ sachet, the standard postharvest treatment. Table grapes stored for 60 days reached 30%, against 100% both untreated and with SO₂.

The trials ran at laboratory scale, and the authors note that a formal biosafety assessment is still needed. The work gives the fruit cold chain cold-active candidates that act at a distance against a Botrytis strain that has already escaped four fungicides.

Researchers at Guizhou University of Traditional Chinese Medicine and Zhejiang University screened 21 commercial surfactants with Metarhizium anisopliae QLSMA201102, a native strain they had previously identified as a candidate against the tomato leafminer Phthorimaea absoluta. Conidia of entomopathogenic fungi are hydrophobic and clump in water, so surfactants are needed to suspend and spray them, yet some can damage the cells.

Several anionic surfactants strongly inhibited germination, and two of them, MOA-9P and SDBS, cut it to 2.62% and 3.42%. Most non-ionic surfactants and biosurfactants did not affect germination, although several of them still slowed colony growth.

Sophorolipid, a biosurfactant, and Tween-80 raised the number of conidia retained on tomato leaves from 232.8 to about 290 per mm². PEG-8000 gave the strongest UV-A protection, with germination above 90% at 0.1% and 0.25%. Sophorolipid at 0.25% nearly doubled germination after 45 minutes at 45 °C, from 36.7% to 69.6%. At 0.5%, all three raised seven-day mortality of third-instar larvae above 91%, against 65.71% for conidia without surfactant.

The tests ran in the laboratory, with larvae dipped in the suspensions rather than sprayed and only three replicates in the larvae test, and greenhouse and field trials are the next step. The study gives formulators a tested shortlist of adjuvants for this strain, and shows that each surfactant has to be tested with the fungus, since surfactants of the same type behaved differently.

Researchers at the State University of Maringá, working with the Brazilian company Ballagro, electrospun a commercial Bacillus amyloliquefaciens fermentation broth (strain CCT 7901) directly into poly(vinyl alcohol) nanofibers. Earlier studies first separated the cells from the broth, often by centrifugation, washing or freeze-drying, and electrospun only the cells. This team skipped those steps and mixed the crude broth with the polymer, and in one formulation the broth was the only solvent.

Keeping the broth improved the fibers. They came out thinner and more uniform, about 325 nm against 478 nm for PVA alone, and tensile strength rose from 5.8 MPa to as much as 9.3 MPa. The authors attribute the finer fibers to biosurfactants in the broth, where mass spectrometry found signals that likely correspond to surfactin, iturin and fengycin.

Viable counts fell from 1.89 × 10⁹ CFU/mL in the broth to 8.33 × 10⁷ CFU/mL in the spinning solution and 3.33 × 10⁷ CFU/cm² in the fibers. After one year in a sealed container at ambient laboratory conditions, fiber fragments still yielded B. amyloliquefaciens colonies, confirmed by MALDI-TOF, although the study did not count how many survived.

Removing centrifugation, washing and freeze-drying from the process is the main promise of the approach. The authors' next step is to compare the fibers with a liquid formulation for bacterial release, root colonization and biocontrol.

BioConsortia, based in Davis, California, raised US$15 million in equity from an existing investor on 9 October, to fund the commercial launch and scale-up of its nitrogen-fixing seed treatment Always N and its biostimulant Zaffre.

Always N is built on spore-forming Paenibacillus bacteria, which the company credits for more than two years of shelf life plus two more on treated seed. It comes in a wild-type and a gene-edited version to fit different regulatory regimes. New Zealand restricts gene-edited organisms, so the product launched there in late 2024 with wild-type microbes, as FixiN 33, through the seed company H&T. In company trials on maize in Brazil, 75% of the recommended nitrogen plus Always N out-yielded the full nitrogen dose.

Offering one product in two versions shows how biological companies are keeping their options open across markets, so a nitrogen fixer can reach growers in whatever form local rules allow, already on the seed.

Neorhizobium galegae bv. orientalis Gr30-13 is a highly effective inoculant strain for goat's rue (Galega orientalis), a forage legume. Researchers at the All-Russian Research Institute for Agricultural Microbiology in Saint Petersburg sowed seed treated with the strain in a plot with no native population of the species. Over the following two years they recovered it from the plants' nodules, and PCR fingerprinting confirmed the isolates were Gr30-13.

Long-read sequencing of ten of these reisolates confirmed genome rearrangements in three. One of them, Re 20-2, carried two tandem duplications, one in a sugar-transport gene on the chromosome and one on the symbiotic replicon.

In a 30-day sterile tube test, all nine reisolates tested gave goat's rue more shoot mass than the original strain. Plants inoculated with the three rearranged reisolates averaged 31% more shoot mass than those inoculated with Gr30-13, against 16% for the six unchanged ones. Re 20-2 gave the largest gain, 35%, and the only one significant on its own.

The authors say that confirming the rearrangements caused the gain needs further study, and they plan mutation and transcriptomic tests of the genes involved. They see a promising breeding route in the approach, letting soil and host select clones of an inoculant strain that work better under local conditions.